Henry Deringer of Philadelphia, PA was one of the most prolific rifle and pistol makers of the first half of the 19th Century. It was one of his company's pocket pistols that was used by Boothe to assassinate President Lincoln.
He was one of the earliest/original suppliers of rifles to the western Indian trade as well as rifles to the US military.
They also made rifles for the "local" trade which is what it sounds like you have. Half-stock rifles became popular in the 1830's here in the states and remained so through the rest of the muzzleloading era.
The name is often misspelled Derringer, which was used by other makers producing knock offs his pistols in particular.